Centrifugal compressing of low molecular weight gases



Dec. 15, 1964 P. G. LA HAYE CENTRIFUGAL COMPRESSING OF LOW MOLECULARWEIGHT GASES Filed April 18, 1965 3 Sheets-Sheet 1 .T 1 3-1- Q6/deff'INVENTOR Dec. 15, 1964 P. G. LA HAYE CENTRIFUGAL COMPRESSING OF' LOWMOLECULAR WEIGHT GASES 5 Sheets-Sheet 2 Filed April 18, 1963 NN hm.

INVENTOR.

12104 67A/ An/5 Dec. l5, 1964 P. G. LA HAYE 3,161,020

CENTRIFUGAL coMPREssING oF Low MOLECULAR WEIGHT GASES Filed April 18,1963 3 Sheets-Sheet 3 3,161,020 CENTRFUGAL CMPRESSHNG F LW MLECULARWEIGHT GASES Paul G. La Haye, Schenectady, NSY., assignor to MechanicalTechnology Incorporated, Latham, NX., a corporation of New York FiledApr. 18, 19673, Ser. No. 273,3S0 1t) Claims. (Qi. @tl- 39.6%

This invention relates to the centrifugal compression of low molecularweight gases, and particularly to improved methods and apparatus foroperating turbines from a source of low molecular weight gaseous fuelwhich, as made commercially available, is under a relatively lowpressure. Gaseous fuel is available from supply mains where the pressureis considerably below that required for injection into gas turbinecombustion systems, but is of low molecular weight and difficult tocompress centrifugally until it exceeds the pressure in the combustionsystem of the turbine. Such fuel is far more difficult to compre-ss to ahigh pressure than is air or other higher molecular weight gases. In thepast, the use of reciproeating or positive displacement compressors hasgenerally been necessary in order to compress the gaseous fuel to theextent necessary to inject it into the combustion zone of a gas turbineand to provide control over the combustion process.

An object of this invention is to provide a relatively simple,inexpensive, safe and practical method and apparatus for centrifugallycompressing low molecular weight gases.

Another object is to provide a more eiiicient performance of the task ofcentrifugally compressing a gaseous fuel of low molecular weight up topressures enabling injection into the combustion zone of a gas turbine,which canbe made available at reasonable shaft speeds and where smallgas quantities are required at high pressure ratios.

A further object of the invention is to provide a simple and effectivemethod and apparatus for centrifugally compressing the gaseous fuel asreceived from the supply mains or other source to the pressure desiredfor injection into the combustion system of a gas operated turbine,which is eiiicient, trouble free, compact, and powered by the turbineunit, and which permits control of primary combustion air so that theposition and intensity of the combustion process can be externallycontrolled to some degree, which eliminates the need for any expensivecompressor and control system to maintain the desired pressure ratio offuel to main-turbine combustor pressure; and to provide a source of lowpressure gas at a reasonable `temperature for use in iiuid seals and asa cooling gas for turbine Wheels andv other components, and which mayprovide a drive for turbine accessories and auxiliaries such as Waterpumps.

A further object is to provide for the combustion of gases with a Wenergy content which cannot in-thernselves maintain combustion, but can,when enriched with a combustible fuel be combustible, and to furtherprovide for the control of the mixture of a low energy gas and highenergy gas to obtain maximum thermal eiciency.

Other objects and advantages will appear from the following descriptionof several embodiments of the linvention, and the novel features will beparticularly pointed out hereinafter in connection with the appendedclaims.

In the accompanying drawings:

United States Patent O FIG. 1 is a schematic diagram of turbineapparatus 3,161,020 Patented Dec. 15, V1964 ICC ugal compressor that maybe employed to compress low molecular weight gases.

In Iaccordance with this invention, a low molecular weight gas, which isdifficult to compress` adequately in centrifugal compressors, is mixedwith a higher molecular weight gas, and this mixture may then be easilyand efficiently centrifugally compressed. For example, commericallyavailable fuel gas is of low molecular weight, and it cannot besuciently compressed in small quantities `in a centrifugal compressorfor injection into combustion systems used to drive turbines. By iirstmixing such low molecular weight gas with air, for example, which has ahigher molecular Weight, in a proportion less than is' necessary tosupport combustion of the mixture, this mixture of air and fuel gas maybe easily centrifugally compressedsufiiciently to enable its deliveryinto the combustor of the combustion system of a gas turbine. Thenecessary compression of a low molecular weight gas, such as a fuel gas,may be easily obtained according to this invention at reasonable shaftspeeds and impeller tip speeds, instead of the use of reciprocating or`positive displacement pumps. The power required for centrifugallycompressing such a premixture of air and gaseous fuel is so small thatthe compression of the air and gas mixture may be obtained `in a simpleand practical manner through energy obtained from the turbine system,either by a direct drive from the shaft or from the expansion of gasfrom the turbine system.

In the embodiment of the invention illustrated in FIG. l, the gaspowered turbine unit, designated generally by reference 1, includes theair inlet hood 2, lea-ding to an air compressor 3 that is operativelycoupled to and driven by one or more turbine wheels or units 4 and 5, anexhaust hood 6, and a coupling or clutch 7 through which the turbinerotor may be drivingly connected to a load 3. 'Ihe load may be connectedto an independent turbine wheel which is not connected mechanically tothe turbine wheel driving the main compressor. The power for operationof the rotor is obtained from combustor means 9 in which the fuel gasand air are burned, and the hot combustion gases delivered therefrom tothe turbine wheels or rotor units d and 5. Air for combustion isdelivered under pressure from the compressor 3 to the combustors 9through passages or pipes 10 and gaseous fuel under pressure isdelivered to the combustors 9 by pipe 11.

Gaseous fuel from a supply source, such as the main 12 of a commercialsupply of natural or manufactured gas or othercombustible gas isWithdrawn through pipe 13 under control of a valve 14 and passed througha mixer or carburetor 15 in which it is mixed with primary air or anyother gas having a higher molecular Weight than the primary fuel, suchas carbon monoxide which in itself is also a fuel and will supplementthe primary fuel, for example, supplied thereto through pipe 16 underthe control vof a valve 17. This mixture of higher molecular weight gasand gaseous fuel is passed by means of a pipe 18 to a centrifugalcompressor 19 having one or more stages of compression with and withoutcooling between stages. In the example illustrated, this compressor 19has two stages 20 and 21 connected by a pipe 22. This compressor 19 ispowered by an auxiliary turbine 23 whose shaft 24 is drivingly connectedto the rotors of the compressor stages 20 and 21. Compressor rotors 29and 21 may also be driven directly by the main turbine shaft. The pipe18 is connected to the inlet .port of the rst compressor stage 20, andafter compression in this stage the mixture is passed through pipe 22 tothe inlet port of the second compressor stage 21. The fully compressedmixture of air and gas is passed by pipe 11 from stage 21 to thecombustors 9 of the main turbine 1. While the turbine 23 that operatesthe multi-stage compressor 19 may be any power source, it is preferablyan auxiliary turbine supplied by energy obtained from the main turbineunit. In this example of the invention, this energy is a diversion ofsome of the compressed air from the compressor 3 through pipe 25 to theinlet of this turbine 23, the outlet of this turbine 23 being connectedto atmosphere by pipe 26. A valve 27 in the air line 25 enables controlof the speed of the compressor 19.

In this example of FIG. 1, air entering the hood 2 is compressed incompressor 3 and delivered to `the combustors or combustor means 9through pipes 10. Gaseous fuel and an amount of air considerably lessthan `the amout required to support combustion of the mixture, and whichamount of air may be called less than the stoichiometric amountnecessary to support combustion of the fuel gas, are mixed in anysuitable mixer or carburetor and compressed in the compressor 19 anddelivered by pipe 11 to the combustors or combustor means 9. Thecompressor 19 is operated by turbine 23 powered by compressed air fromthe compressor 3. The primary air which is mixed with the gaseous fuelmakes the compression of the fuel very much simpler and easier becausethe air adds suiiicient molecular weight to the mixture to enable itsfull and easy compression to the extent or pressure necessary for itsinjection into the combustors. While the amount of primary air added tothe gaseous fuel must, for safety, be less than that necessary tosupport combustion of the mixture, i.e., less than the stoichiometricmixture for combustion, I have found that about half of the amount ofair necessary to support combustion of the fuel gas gives adequate andexcellent compressibility to the mixture, without danger of explosion orpremature combustion of the mixture, even if there should be some airleakage into the mixture before it enters the combustors 9. Thecompression of the fuel air mixture may be now easily accomplished in aconventional or any centrifugal compressor at top speeds and shaftspeeds which are within present day technical capabilities, such asapproximately 60,000 r.p.m. and tip speeds below 1400 ft./sec., andwithin .the limitations imposed by the materials used or available.

In the embodiment of the invention illustrated in FIG. 2, theconstruction is similar to that shown in FIG. l, and identical partshave the same reference numerals in both FIGS. 1 and 2. The maindifference between FIGS. l and 2 is .that whereas the pipe 25 of FIG. 1was connected directly to the air compressor 3, in FIG. 2 it isidentified by reference numeral a and is connected instead to one of thestages of the main turbine, such as to the first stage 4, so that someof the combustion gases that drive the turbine wheel in the first stage4, instead of going to the second stage 5, are diverted to the auxiliaryturbine 23 for the compression of the fuel air mixture.

In the embodiment of the invention illustrated in FIG. 3, the differencefrom FIGS. 1 and 2, is that the pipes 25 and 25a of FIGS. 1 and 2,respectively, are replaced by a pipe 25C that is connected to the mainair compressor 3 to receive compressed air therefrom, and is passedthrough a heat exchanger 28 disposed in the exhaust hood 6, and thenthrough valve 27 to the auxiliary turbine 23. The compressed airreceived from compressor 3 is heated in the exhaust hood by heatexchanger 2S, where .the air receives further energy in the form ofheat, and then the heated air is delivered to the auxiliary turbine 23to operate the latter.

In the embodiment of the invention illustrated in FIG. 4, thearrangement is the same as in FIGS. 1-3 except that pipes 25, 25h, and25e of FIGS. 1-3, respectively, are replaced with another pipe 25d withcontrol valve 27 therein. One end of pipe 25d is connected to the mainair compressor 3 to receive compressed air therefrom, and this airisdelivered to an auxiliary combustor 29. A branch pipe 30 having acontrol valve 31 therein connects pipe 11 to the auxiliary combustor 29,and some of the compressed air and gaseous fuel from compressor stage 21is supplied to the auxiliary combustor 29 where it burns with the aid ofthe secondary air from the compressor 3. The gases of combustion fromcombustor 29 are delivered by pipe 32 to auxiliary turbine 23 to operateit. Branch pipe 30 may be connected directly to fuel gas header 12rather than pipe 11 when the gas pressure in (12) is greater than inpipe (25d), thereby simplifying the control of fuel to the auxiliarycombustor.

The operation of the embodiments shown in FIGS. 24 is generally the sameas explained for the embodiment shown in FIG. l, except as particularlypointed out in connection with each figure.

The air exhausted from the turbine 23 (FIGS. l and 3), instead of beingexhausted to atmosphere, may be conducted to fluid seals of turbinesadjacent the turbine bearings to replace the air supply now provided forthe seals adjacent to the bearings for preventing escape and loss oflubricants from the bearings, and also may be used to cool turbinewheels.

In the embodiment of the invention illustrated in FIG. 5, the apparatusthere shown may be used to compress easily and with a minimum of power,Iany low molecular weight gas by first mixing it with a higher molecularweight gas, and then centrifugally compressing such mixture. As anexample, it may be used to compress the low molecular weight fuel gas,such as is available in commercial fuel gas mains, by mixing it w-ithair in an amount insufficient to support combustion of the fuel gas, andthen compressing it in a two-stage compressor and delivering it to aturbine combustor. It is a physical illustration of suitable mixing andcompressing means for the fuel gas and air that is illustrated onlyschematically in FIGS. 1-4, but which may be employed to mix any lowmolecular weight gas with any higher molecular weight gas, and compressthe mixture centrifugally for any purpose.

In FIG. 5, the low molecular Weight gas or primary fuel which it isdesired to centrifugally compress, such as natural or manufactured gas,for example, is supplied to the compressing apparatus by conduit 33, andthe higher molecular Weight or secondary gas, which may be a fuel thatdoes not burn by itself but increases the molecular weight of themixture when mixed with the primary fuel, is supplied to the compressingapparatus by conduit 34. Examples of this secondary or higher molecularweight gas are air, blast furnace tail gases, and other low energycontent but high molecular weight fuel gas. The primary gas or fuelsupplied by conduit 33 is delivered by a nozzle 35 into an extension 36of the conduit 34 diverging in the direction of flow of the gas inconduit 34. The proportions of the primary and secondary gases in themixture may be controlled by a tapered control rod 37 disposed in thenozzle 35. The rod 37 is adjustable in a direction lengthwise of itselfto move its tapered free end to various extents through the dischargeorifice of the nozzle, and thus vary selectively the amount of primaryor low molecular weight gas which is introduced into and mixes with thestream of the secondary or higher molecular weight gas. The conduit 36as it becomes progressively larger in diameter in a direction away fromthe nozzle 35, delivers the mixture to the intake port 38 of thetwo-stage centrifugal compressor illustrated.

This compressor includes a main shaft 39 rotatably mounted near itsopposite ends in suitable bearings 40 in a housing 41. Fixed on theshaft 39 are a first stage impeller or rotor 42 with vanes or blades 43,and a second stage impcller or rotor 44 with vanes or blades 45 arrangedin succession along the shaft 39. Further along the shaft 39 and fixedon its free end is a turbine disc 46 provided at its periphery with aplurality of turbine blades or buckets 47 arranged in spaced apartrelation along the periphery of the disc 46. The disc 46 is enclosed ina housing 48 which tapers to a peripheral channel 49 in close clearancewith the disc 46, with the buckets 47 extending through the channel intoa conduit 50 that extends crosswise or axial of the disc 46 andprogresses crosswise of the disc 46 against the buckets or blades 47 tocause rotation of the disc 46 and through it of the shaft 39. Theconduits u lead from the disc 46 to a collector 54 that is connected toan exhaust conduit 58 that in turn leads to seals, to cooling or toatmosphere.

The mixture of gases from conduit 36, upon entering the intake port 38,is discharged through an annular intake passage 56 against the radiallyinner ends of the vanes 43 and these rotating vanes force the gasmixture radially outward into and through a narrow passage 57 havingacross it a plurality of diffuser vanes 58a. The passage 57 then leadsradially towards the shaft 39 and discharges its gases that werecompressed in the first stage by vanes 43 against the inner ends of thevanes 45 of rotor impeller 44 that is fixed on rotary shaft 3%. Thevanes 45 lead outwardly to the periphery of the second stageiimpeller 44and are delivered, further compressed, into la passage 59 having acrossit diffuser vanes 60. The passage 59 discharges this further compressedgas mixture into an annular collector 61 which has an outlet pipe 62which leads to the combustors of the main gas turbine.

|This compressor of FIG. 5 has been explained in connection with gasturbines where it has a very important use, but it can be used, when theturbine 46 is driven by any compressed gas or replaced by other motivemeans, to centrifugally compress with a low power consumption, a mixtureof any low molecular weight gas and any gas of higher molecular Weight.

It will be understood that various changes in the details, materials,steps and -arrangements of parts which have been herein described andillustrated in order to explain the nature of the invention, may be madeby those skilled in the art Within the principle and scope of theinvention as. expressed in the appended claims.

I claim:

1. A gas turbine system using a centrifugal compressor for supplying agaseous fuel supply to a gas turbine, comprising:

(a) a gas turbine unit having a compressor, a combustor, and a turbine,said turbine being connected to said compressor and having an outputshaft;

(b) a gaseous fuel compressor unit having a centrifugal compressorassembly for compressing and delivering a gaseous fuel mixture to saidcombustor at a pressure slightly higher than the pressure in saidcombustor;

(c) a turbine forming part of said gaseous fuel cornpressor unitconnected to said centrifugal compressor assembly and having a highlpressure gas supply line connected to said gas turbine unit foreffecting movement of said turbine;

(d) carburetor means connected to said compressor assembly for supplyinga mixture of gaseous'fuel thereto;

(e) a low molecular weight gaseous fuel supply conduit connected to saidcarburetor means at one end and having its other end connected to acommercial fuel gaseous supply main containing high energy low molecularweight fuel gas at a pressure slightly higher than atmospheric pressure;

(f) a secondary gas lconduit containing a high molecular weight gasconnected to said carburetor means; and

(g) control means associated with said carburetor for controllingmixture of said gases to produce a relatively high molecular weightgaseous fuel mixture, whereby said centrifugal compressor is able toraise 6 the pressure of said mixture above that in the combustor of saidgas turbine unit at a high eiciency, and to deliver it to the combustorof said gas turbine unit.

2. The gas turbine system using a centrifugal compressor for supplying agaseous fuel supply to a gas turbine as set forth in claim 1 whereinsaid secondary conduit contains air and said carburetor means mixes saidair with said low molecular weight gaseous fuel in an amountconsiderably less than is necessary to support combustion.

3. The gas turbine system using a centrifugal compressor for supplying agaseous fuel supply to a gas turbine as set forth in claim l wherein thecompressor of said gas turbine unit is connected to said high pressuregas supply line for the turbine of said gaseous fuel compressor unit.

4. The gas turbine system using a centrifugal compressor for supplying agaseous fuel supply to a gas turbine as set forth in claim 1 whereinsaid high pressure gas supply line connected to the turbine of saidgaseous fuel compressor unit has a heat exchanger therein for heatingythe gas supplied to said turbine.

5. The gas turbine system using a centrifugal compressor for supplying agaseous fuel supply toa gas turbine as set forth in cl-aim 1 whereinsaid centrifugal compressor assembly comprises a first and a secondcentrifugal compressor stage.

6. The gas turbine system using a centrifugal compressor for supplying agaseous fuel supply to a gas turbine as set forth in claim 1, whereinsaid gaseous fuel compressor unit has a central shaft on which saidturbine and said centrifugal compressor assembly are integrally mounted.Y

7. The gas turbine system using a centrifugal compressor for supplying agaseous fuel supply to a gas turbine as set forth in claim l, whereinSaid carburetor means is formed by the juncture of said fuel gas supplyconduit and said secondary gas conduit, and said control means comprisesa tapered movable rod in said low molecular weight fuel gas supplyconduit for controlling the supply of low molecular Weight fuel gas.

8. The method of supplying gas fuel of low molecular Weight from `arelatively low pressure source to a gas turbine having a combustor whichreceives compressed air at a high pressure from the gas turbinecompressor unit, which comprises:

(a) mixing said low pressure low molecular weight high energy gaseousfuel with a low energy high molecular weight gas in suiicient proportionto give a relatively high energy and high molecular weight gaseous fuelmixture;

(b) centrifugally compressing said gaseous fuel mixture to a pressuregreater than that in the combustor section of the gas turbine;

(c) adding sufficient air to said compressed gas mixture to make itcombustible;

(d) burning this mixture of compressed gases with said air; and

(e) operating a turbine with said burned gases.

9. The method of operating 'a gas turbine from a relatively low pressuresource of high energy low molecular Weight gaseous fuel as set forth inclaim 8, and effecting the centrifugal compression of said low and highmolecular weight gases with energy from said turbine.

l0. A method of supplying gas fuel 0f low molecular weight from arelatively low pressure source to .a gas turbine having a combustorwhich receives compressed air at a high pressure from the gas turbinecompressor unit, which comprises:

(a) mixing said low pressure low molecular weight high energy gaseousfuel with air in sutiicient proportion to give a relatively high energyand high molecular Weight .4 gaseous fuel mixture, the amount of airbeing considerably less than necessary for combustion of such mixture;

(b) centrifugally compressing said gaseous fuel mixture to a pressuregreater than that in the combustor 5 section of the gas turbine solelyby centrifugal means and by at least one centrifugal stage compressor;

(c) adding suicient air to said compressed gas mixture to make itcombustible;

(d) burning this mixture of compressed gases with 10 said air; and

(e) operating a turbine with said burned gases.

References Cited in the file of this patent UNTED STATES PATENTS McKeeDec. 8, Garretson July 3, Traupel Nov. 29, Sedille Dec. 16, Forsling May11, Torell Jan. 24, Shannon et al Mar. 11, Grifth May 23, Schropp July11,

Flanders Sept. 24,

1. A GAS TURBINE SYSTEM USING A CENTRIFUGAL COMPRESSOR FOR SUPPLYING AGASEOUS FUEL SUPPLY TO A GAS TURBINE, COMPRISING: (A) A GAS TURBINE UNITHAVING A COMPRESSOR, A COMBUSTOR, AND A TURBINE, SAID TURBINE BEINGCONNECTED TO SAID COMPRESSOR AND HAVING AN OUTPUT SHAFT; (B) A GASEOUSFUEL COMPRESSOR UNIT HAVING A CENTRIFUGAL COMPRESSOR ASSEMBLY FORCOMPRESSING AND DELIVERING A GASEOUS FUEL MIXTURE TO SAID COMBUSTOR AT APRESSURE SLIGHTLY HIGHER THAN THE PRESSURE IN SAID COMBUSTOR; (C) ATURBINE FORMING PART OF SAID GASEOUS FUEL COMPRESSOR UNIT CONNECTED TOSAID CENTRIFUGAL COMPRESSOR ASSEMBLY AND HAVING A HIGH PRESSURE GASSUPPLY LINE CONNECTED TO SAID GAS TURBINE UNIT FOR EFFECTING MOVEMENT OFSAID TURBINE; (D) CARBURETOR MEANS CONNECTED TO SAID COMPRESSOR ASSEMBLYFOR SUPPLYING A MIXTURE OF GASEOUS FUEL THERETO; (E) A LOW MOLECULARWEIGHT GASEOUS FUEL SUPPLY CONDUIT CONNECTED TO SAID CARBURETOR MEANS ATONE END AND HAVING ITS OTHER END CONNECTED TO A COMMERCIAL FUEL GASEOUSSUPPLY MAIN CONTAINING HIGH ENERGY LOW MOLECUALR WEIGHT FUEL GAS AT APRESSURE SLIGHTLY HIGHER THAN ATMOSPHERIC PRESSURE; (F) A SECONDARY GASCONDUIT CONTAINING A HIGH MOLECULAR WEIGHT GAS CONNECTED TO SAIDCARBURETOR MEANS; AND (G) CONTROL MEANS ASSOCIATED WITH SAID CARBURETORFOR CONTROLLING MIXTURE OF SAID GASES TO PRODUCE A RELATIVELY HIGHMOLECULAR WEIGHT GASEOUS FUEL MIXTURE, WHEREBY SAID CENTRIFUGALCOMPRESSOR IS ABLE TO RAISE THE PRESSURE OF SAID MIXTURE ABOVE THAT INTHE COMBUSTOR OF SAID GAS TURBINE UNIT AT A HIGH EFFICIENCY, AND TODELIVER IT TO THE COMBUSTOR OF SAID GAS TURBINE UNIT.